Embodiments are related generally to a Lateral Double Diffused Metal-Oxide-Semiconductor (LDMOS) semiconductor device.
Since a related art power Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) has high input impedance compared to a bipolar transistor, power gain is high and a gate drive circuit is simple. Additionally, since the related art power MOSFET is a unipolar device, there is no time delay occurring due to accumulation or recombination by minority carriers during turn-off.
Accordingly, as a current trend, the related art power MOSFET is gradually and extensively applied to a switching mode power supply unit and a lamp stabilization and motor drive circuit.
The related art power MOSFET generally has Doubled Diffused MOSFET (DMOS) structure using a planar diffusion technique and its representative one is a Lateral Double Diffused Metal-Oxide-Semiconductor (LDMOS).
In a case of the LDMOS, when a drain has lower electric potential than a substrate at a low side, a P-N junction operates in a forward direction. Consequently, noise occurs.
In order to remove the noise, the LDMOS includes a single-type or double-type deep well guardring and a floating-type structure.
In a case of the single-type guardring, however, it is insufficient to completely block electrons. Moreover, in a case of a double-type guardring, the ability of collecting electrons is excellent but a chip size is greatly increased.
In a case of the floating type structure, when medium current is injected, it effectively collects electrons. When high current is injected, however, the ability of collecting electrons is drastically deteriorated.